1. Field of the Invention
The present invention relates to check valves or safety relief valves for use with flexible containers for use with coffee. Relief valves allow excess pressure in a container to be relieved while not allowing outside air into the container.
2. Description of Related art
Fresh roasted coffee gives off carbon dioxide (CO2) for an average of twenty-two (22) days after roasting. A relief valve is required when using flexible containers to store and transport freshly roasted coffee due to the pressure build up of the CO2 within the container. Without a relief valve flexible containers have been known to burst due to the gas pressure buildup. Use of relief valves allows a coffee roaster to package coffee immediately after roasting instead of having to store the coffee for three to five (3-5) days.
Relief valves have to function whether whole bean or ground coffee is placed in the flexible containers. In the case of ground coffee, small grains of coffee can cause a relief valve to stop functioning which in turn causes the container to inflate with CO2 and potentially burst. A simple, economical, relief valve is the object of the present invention.
Various forms of relief valves have been used with some success. One such valve is disclosed in U.S. Pat. No. 4,420,015, issued Dec. 13, 1993 to Hans Blaser. This valve utilizes a valve body having a carrier plate with a lateral edge flange with a central shallow recess for receiving a flexible diaphragm and a clamping member with jaws that is held in place by an inside rim of the recess. The diaphragm is made of a very thin soft plastic such as a polyester film. A silicone oil is used between the diaphragm and a valve seat within the recess. The silicone oil is used to help ensure a secure seal.
Another such valve is disclosed in U.S. Pat. No. 3,595,467, issued on Jul. 27, 1971 to Luigi Goglio. The valve disclosed therein includes a hollow body which is provided with a passage and is formed of a base member ultrasonically welded to a bag and a hollow member forming a cover. The cover has a centrally disposed projection with which a flexible resilient disc is pressed against the passage in the base member. When there is excess CO2(gas) pressure in the container, the disc is lifted away from the base member at the opening and CO2 can flow through the passage to be discharged through the opening in the cover. One draw back of such a valve is that when the valve is manufactured the parts must be assembled in a particular manner keeping the parts centered in relation to each other. Such precise alignment of various parts, where a distinction must be made between top and bottom on some parts, requires additional mechanisms on packaging machines which add to the cost of manufacturing such bags.
Another valve design is disclosed in U.S. Pat. No. 3,799,427 issued on Mar. 26, 1974 to Luigi Goglio. This patent discloses an improved valve in which a conical abutment is placed in the region of the passage opening and a viscous intermediate layer is added between the valve member and valve seat. Although this provides a better distinction between the open and the closed positions of the valve, the above-mentioned drawbacks continue to exist.
There remains several problems with the valve designs noted above. First, they require three or more parts that must be assembled. In addition, they each use a filter that must be attached to the side of the valve facing or in contact with the contents of the container, such as ground coffee. Each valve requires a certain degree of precision in forming the parts in order for them to fit together and work properly. The proceeding problems increase the cost and reliability of the valves.